The last time short interest in the SPDR S&P 500 ETF was this low was in early October 2018, just when everyone was preparing for lift-off and the Santa rally and what not, and short-sellers didn’t want to be caught on the wrong side of the trade. But instead, all heck broke loose.

It turned into the worst October anyone could remember, and a near-20% sell-off of the S&P 500 Index by Christmas.